This hop filter is a coarse filter of stainless steel mesh. It sits above the valve in your BrewTub and is placed at the beginning of the brew during setup. This filter allows copious amounts of hops, fruits, coffee, and other large particle size additions to be made directly to the BrewTub. When the SqueezeBar is released, the Hop Filter prevents the large particle additions from flowing into your bag, resulting in a finished bag of beer that is free from any unwanted floaters.